Biology subjects

Elkholi, I. E.

Publications and source records attributed to Elkholi, I. E..

3 recordsLinked to original sources

bioRxiv2023

Targeting the dependence on PIK3C3-mTORC1 signaling in dormancy-prone breast cancer cells blunts metastasis initiation

Halting breast cancer metastatic relapses following primary tumor removal and the clinical dormant phase, remains challenging, due to a lack of specific vulnerabilities to target during dormancy. To address this, we conducted genome-wide CRISPR screens on two breast cancer cell lines with distinct dormancy properties: 4T1 (short-term dormancy) and 4T07 (prolonged dormancy). We discovered that loss of class-III PI3K, Pik3c3, revealed a unique vulnerability in 4T07 cells. Surprisingly, dormancy-prone 4T07 cells exhibited higher mTORC1 activity than 4T1 cells, due to lysosome-dependent signaling occurring at the cell periphery. Pharmacological inhibition of Pik3c3 counteracted this phenotype in 4T07 cells, and selectively reduced metastasis burden only in the 4T07 dormancy-prone model. This mechanism was also detected in human breast cancer cell lines in addition to a breast cancer patient-derived xenograft supporting that it may be relevant in humans. Our findings suggest dormant cancer cell-initiated metastasis may be prevented in patients carrying tumor cells that display PIK3C3-peripheral lysosomal signaling to mTORC1. Statement of SignificanceWe reveal that dormancy-prone breast cancer cells depend on the class III PI3K to mediate a constant peripheral lysosomal positioning and mTORC1 hyperactivity. Targeting this pathway might blunt breast cancer metastasis.

cancer biology↗

bioRxiv2023

Mapping the MOB proteins' proximity network reveals a unique interaction between human MOB3C and the RNase P complex

Distinct functions mediated by members of the monopolar spindle-one-binder (MOB) family of proteins remain elusive beyond the evolutionary conserved and well-established roles of MOB1A and B in regulating the Hippo pathway. Since MOB proteins are adaptors, understanding how they engage in protein-protein interactions and complexes assembly is essential to define the full scope of their biological functions. To address this, we undertook a proximity-dependent biotin identification (BioID) approach to define the interactomes of all seven human MOB proteins in HeLa and HEK293 cell lines. We uncovered > 200 interactions, of which at least 70% are unreported on BioGrid. The generated dataset reliably recalled the bona fide interactors of the well-studied MOBs. We further defined the common and differential interactome between different MOBs on a subfamily and an individual level. We discovered a unique interaction between MOB3C and 7 out of 10 protein subunits of the RNase P complex, an endonuclease that catalyzes tRNA 5 maturation. As a proof-of-principle for the robustness of the generated dataset, we validated the specific interaction of MOB3C with catalytically active RNase P by using affinity purification-mass spectrometry and pre-tRNA cleavage assays of MOB3C pulldowns. In summary, our data provide novel insights into the biology of MOB proteins and reveal the first interactors of MOB3C, components of the RNase P complex, and hence an exciting nexus with RNA biology.

biochemistry↗

bioRxiv2021

Interphase microtubule disassembly is a signaling cue that drives cell rounding at mitotic entry.

Reorganization of the cortical actin cytoskeleton at mitotic entry is essential to increase membrane tension for cell rounding1,2. This spherical shape is necessary for the biogenesis and organization of the mitotic spindle2-6. Proteins of the Ezrin, Radixin, Moesin (ERM) family play essential roles in mitotic morphogenesis by linking actomyosin forces to the plasma membrane2,3,7-10. While ERMs drive metaphase cell rounding, the cell-cycle signals that prompt their conformational activation in mitosis are unknown11. We screened a library of small molecules using novel ERM biosensors12 and we unexpectedly found that drugs that disassemble microtubules promote ERM activation. Remarkably, cells disassemble their interphase microtubules while entering mitosis13. We further discovered that this disassembly of microtubules acts as a cell-cycle signal that directs ERM activation and metaphase cell rounding. We show that GEF-H1, a Rho-GEF inhibited by microtubule binding, acts downstream of microtubule disassembly to activate ERMs via RhoA and its kinase effector SLK. In addition, we demonstrate that GEF-H1 and Ect2, another Rho-GEF responsible for the generation of mitotic actomyosin forces6,14, act together to drive metaphase ERM activation and cell rounding. In summary, we report microtubule disassembly as a cell cycle signal that triggers a signaling network ensuring that actomyosin forces are efficiently integrated at the plasma membrane to promote cell rounding at mitotic entry.

cell biology↗